Internal combustion engine ignition system

ABSTRACT

A plurality of permanent magnets forming a cylinder is rotated about a common axis, inducing voltages in two windings on respective legs of a magnet yoke positioned within the cylinder, the windings being so wound that their voltage normally cancel. Means are provided within the cylinder so as to upset, once every rotation of the plurality of magnets, the balance between the voltages in the two windings so that there is produced a control voltage that is conducted to the control electrode of a thyristor that controls the discharging of an ignition capacitor through the primary of a spark coil. In one form of the invention, the cross piece connecting together the two legs is nonmagnetic, and means are provided for preventing the generation of a control voltage when the engine rotates in the wrong direction.

United States Patent 1 Imhof et a1.

[ INTERNAL COMBUSTION ENGINE [73] Assignee: Robert Bosch GmbII, Stuttgart,

Germany [22] Filed: July 12, 1971 [21] Appl. No.: 161,766

[30] Foreign Application Priority Data July 28, 1970 Germany P 20 37 336.8

[52] 11.8. C1. 123/148 E, 123/149 D, 123/148 R [51] Int. Cl F02p 1/00 [58] Field 01' Search 123/148 E [56] References Cited UNITED STATES PATENTS 3,623,467 11/1971 Piteo 123/148 E 3,517,655 6/1970 .laulmes 123/148 E 3,630,185 12/1971 Struber 123/148 E 3,646,667 3/1972 .lanisch 123/148 E 3,599,615 8/1971 Foreman 123/148 E [111 3,753,429 [451 Aug. 21, 1973 3,598,098 8/1971 Sohner 123/148 E Primary ExaminerLaurence M. Goodridge Assistant ExaminerRonald B. Cox Attorney-Michael S. Striker [5 7] ABSTRACT A plurality of permanent magnets forming a cylinder is rotated about a common axis, inducing voltages in two windings on respective legs of a magnet yoke positioned within the cylinder, the windings being so wound that their voltage normally cancel. Means are provided within the cylinder so as to upset, once every rotation of the plurality of magnets, the balance between the voltages in the two windings so that there is produced a control voltage that is conducted to the control electrode of a thyristor that controls the discharging of an ignition capacitor through the primary of a spark coil. In one form of the invention, the cross piece connecting together the two legs is nonmagnetic, and means are provided for preventing the generation of a control voltage when the engine rotates in the wrong direction.

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Alumna f/reir/frrapAwy INTERNAL COMBUSTION ENGINE IGNITION SYSTEM BACKGROUND OF THE INVENTION The invention relates to an electronic ignition system for an internal combustion engine, the sparking of the one or more spark plugs being controlled by a control voltage that is induced in a control winding carried by a magnet yoke and conducted to the control electrode of an electronic switch, such as a thyristor.

Among these electronic ignition systems of the prior art, it is known to provide a rotatable magnetic system, which comprises a plurality of magnets that, with respect to the axis of rotation, are radially polarized and are mounted on a hollow, cylindrical, short circuiting part. These magnets are spaced apart in the direction of the circumference of the cylindrical short circuiting part. The polarity of these magnets alternates, there being an alternating current winding carried by an iron core, in which winding an alternating current is induced when the magnets rotate. Two lines, each drawn from the axis of rotation through the center of a respective end face of the core, lie along different radiiof the cylindrical short circuiting part, which latter is part of a cup-shaped body of rotation, which has an inwardly extending connecting hub.

Internal cobustion engines that are provided with an ignition system of this kind are usually intended for modern light motorcycles, the current being provided by a flywheel magneto or by a flywheel generator magneto so as to avoid the necessity of having a battery. The aforesaid alternating current winding can be used, for example, to charge the ignition capacitor, which, by triggering the aforesaid electronic switch, can be discharged through the primary winding of a spark coil, the sparkplug being connected across the secondary winding of this coil. To power the lamps and the horn there is usually provided a second alternating current winding carried by another iron core. The same magnetic system induces an alternating current in the second winding. In order to obtain an alternating current voltage of sufficiently high frequency, the magnetic system must have as many magnets as possible. If these same magnets would be used to induce the control voltage in the aforesaid control winding, the control voltage would cause too many ignitions and at times that would damage the engine, since in most cases only a single ignition is required for each complete rotation of the magnetic system.

With these electronic ignition systems of the prior art, there is provided a further rotatable magnet that ismoved past the magnet yoke carrying the control winding at the ignition point. This ensures that the spark plug is sparked only when the piston in the cylinder is sufficiently near to top dead center. To avoid troublesome leakage flux, this further magnet is enclosed by a magnetic shield, a fact that adds to the cost and complexity of the ignition system.

SUMMARY OF THE INVENTION An object of the invention is an electronic ignition system for an internal combustion engine that avoids a special magnet for obtaining the ignition control voltage.

Briefly, the invention consists of a magnetic system, the magnetic system including a plurality of permanent magnets spaced about a common axis and defining a cylinder, means for mounting this plurality of magnets free to be driven in rotation by the engine about the common axis, an electronic switch, such as a thyristor, for permitting when conductive the production of an ignition causing spark, a stationary magnet yoke located within the cylinder, this yoke including two spaced legs that extend radially within the cylinder, a contro winding located within the cylinder and connected to the switch for generating a control voltage to control the conductivity of the switch, the control winding having first and second winding sections to have induced therein voltage components when the plurality of magnets rotates, each leg carrying a respective one of the first and second winding sections, the first and second winding sections being so connected together that normally the voltage components are at least sufficiently balanced out so as to prevent the generation of the control voltage for the switch, and means comprised by the magnetic system for at least sufficiently nullifying the voltage balance between the first and'second winding sections so as to permit the generation of the control voltage at least once every complete rotationof the plurality of magnets. v

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly cut away, of the ignition system and of the magnetic system of the invention;

FIGS. 2 and 3 are side views showing, in a simplified form, two different embodiments of the magnetic circuit;

FIGS. 4, 5, and 6 are top views showing three different variations of the embodiment shown in FIG. 3;-

FIG. 7 is a side view showing a still further variation of the embodiment shown in FIG. 3;

FIG. 8 is a view taken along line 8-8 of FIG. 7;

FIG. 9 is a side view showing another form of the magnetic circuit;

FIGS. 10, 11 and 12 are front views of the magnet M3 of three different variations of the embodiment shown in FIG. 9;

FIGS. 13 and 14 are side views of two different embodiments of the yoke for carrying the control winding;

FIG. 15 is a side view of a yoke having a nonmagnetiferous cross piece; and

FIGS. 16, 17 and 18 are side views of the magnetic circuit shown in FIG. 1, for preventing rotation of the engine in the wrong direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, the ignition system illustrated, which is intended for an internal combustion engine, not shown, comprises an ignition capacitor 11 of which one plate is connected to the ground rail 12 and the other plate is connected to the cathode of a rectifier 13. The anode of the rectifier 13 is connected to one terminal 14 of an alternating current winding 15, which serves as the charging winding, the other terminal 16 of this winding being connected to the ground rail 12. The

ungrounded plate of the ignition capacitor 11 is also connected by the primary winding 17 of a spark coil 18 to the output electrode 19 of a thyristor that operates as an electronic switch 20, the reference electrode 21 and the control electrode 22 of the thyristor respectively being connected to the ground rail 12 and to the cathode of a control diode 23. The anode of the control diode 23 is connected to the control terminal 24 of a control winding 25, the reference terminal 26 of which is connected to the grounded rail 12. The spark coil 18 also includes a secondary winding 27 across which is connected the spark plug 28, one end of the secondary being connected to the grounded rail 12.

The alternating current winding is mounted on an iron core 29, and is located along a chord of a circular path along which move the magnets M of a magnetic system M, the magnets being moved in the direction of the arrow P by the internal combustion engine. Each of the magnets M (three being shown, although there are four in this particular embodiment) is in the form of a shell, the outer faces of which are fixed to the inner wall of a hollow, cylindrical, magnetic short circuiting part 30. This part is a component of a cup-shaped body of revolution K, which is made of a magnetiferous material and incorporates a central, downwardly projecting, hub 31. The hub 31 incorporates a central bore 32, which accepts a shaft 33 that is rotated by the internal combusion engine. Housing with its hub 32 and the shaft 33 constitute rotary support means for the permanent magnets.

The magnets M are radially polarized, as shown in FIG. 1, the north and south poles being designated by the respective reference letters N and S. The magnets M are spaced from one another a distance Z in the direction of rotation, the active" poles (those poles nearest to the ends 34 and 35 of the core 29) of successive magnets being of alternating polarity as they are moved by the end faces 34 and 35. The angle a defined between the radii r1 and r2, which begin at the axis of rotation O and pass through the centers a1 and a2 of these end faces, is so chosen that when a N pole passes by the end face 34 an S pole passes by the end face 35, or the reverse is true, or else when a spacing Z passes by the face 34 another spacing Z passes by the face 35. The alternating current winding 15. and the iron core 29 therefor are mounted on a stationary support means, here in the form of a ciruclar plate 36, which is rigidly fixed to the internal combustion engine, and which incorporates a central opening 37 for the hub 31 and the shaft 33.

Also fixed to the plate 36 is a yoke H, which carries the control winding 25. The yoke H, which is located between the hub 31 and the magnets M, has two legs 38 and 39 that extend in the same radial direction and are spaced apart in the direction of the axis 0, each leg carrying a respective winding section 25' and 25" of the control winding 25. These two legs are at least approximately bar-shaped members. These two winding sections are connected together so as to balance out the voltage components that are induced in them when the magnets M are rotated. To obtain the control voltage for triggering the switch 20, the balance between these voltage components is nullified by changing the magnetic flux, the resulting voltage being used as the control voltage.

This change in the magnetic flux is obtained, in the embodiment shown in FIGS. 1 and 2, by two neighboring magnets M1 and M2 of the magnets M. The magnets M1 and M2 have each a respective tongue-like extension 40 and 41 of a respective S and N pole, these extensions projecting into the common space 2 between these two magnets. Both extensions 40 and 41 are spaced in the axial direction, just as are the legs 38 and 39; and in a predetermined rotational position of the magnets M1 they are aligned with, or cover, respective ones of the end faces 42 and 43 of the legs 38 and 39, which face the magnets M. The radially polarized magnets constitute first permanent magnet means in this embodiment, and the tongue-like extensions 40, 41 together with the respective adjoining portions of magnets MI' and M2 constitute second permanent magnet means in this embodiment.

In the preferred embodiment each of the active poles of the magnets M is covered with a magnetiferous plate L, the respective plates L1 and L2 for the magnets M1' and M2 having each a respective tongue 44 and 45, which extends at least approximately concentrically with the part 30. These tongues constitute, in a very simple manner, the extensions 40 and 41.

The bar-shaped legs 38 and 39 of the yoke H are magnetically connected together by a cross piece 46. In the present embodiment, the cross piece, which extends parallel to the axis 0, connects together those two ends of the legs 38 and 39 that are nearest to the hub 31.

The one winding end 47 of the winding section 25 forms the control connection 24, and the one winding end 48 of the other winding section 25" forms the reference connection 26. With respect to the control connection 24 or the reference connection 26, the two winding sections, looking towards the hub 31, are wound in the same direction. The number of turns of each winding section is such that the voltage components induced in the two winding sections are at least approximately equal when the magnets M without the extensions 40 and 41 move by. The ends 49 and 50 of the winding sections 25 and 25" are connected together. A capacitor C is connected between the control connection 24 and the reference connection 26 to short circuit high frequency interference voltages.

In the following embodiments, those parts that have the same function as in the embodiment shown in FIGS. 1 and 2 are denoted by the reference numerals that are used in the first embodiment, and will not be further described.

With reference to the embodiment shown in FIG. 3, the extensions 40 and 41 and the plates L are omitted. The desired change in flux is obtained by a projection 51 on the hub 31. The projection is turned by one of the end faces 42 or 43 of the legs 38 and 39 in the present embodiment the face 43-, the projection 51, the hub, and the body K all being of a magnetiferous material. The projection 51 is positioned on the hub so that it is located radially oppositeone of the magnets M. In contradistinction to the embodiment shown in FIGS. 1 and 2, the cross piece 46 and the corresponding ends 38 and 39' of the legs 38 and 39 are spaced away from the hub 31. In the simplest case, shown in FIG. 4, the projection 51 is a stud, of which, when it is opposite the end face 43, the cross section is located at least approximately in the position of the cross section of the leg 39.

The leading edge of the control voltage has a favorable shape if, as shown in FIG. 5, the projection 51, in

the direction of rotation P, converges towards the hub 31. A stepped ignition advance is obtained with the variation shown in FIG. 6, in which a magnetiferous projection 52, which has a smaller effect on the amount of flux that passes through the leg 39 than the projection 51, is provided on the hub 31 so as to precede the pin 51 in the direction of rotation. The desired smaller magnetic efiect can be obtained by making the projection 52 of a material having a higher reluctance than the material of the projection 51, or the projection 52 can have a smaller cross section than the projection 51, or the projection52 can be spaced farther from the leg 39 than is the projection 51. In the example illustrated in FIG. 6, the projection 52 is spaced farther from the leg 39 than is the projection 51.

To obtain the desired change in magnetic flux, the hub 31 can be provided, as shown in FIGS. 7 and 8, with at least one recess 53, instead of the projection 51 or the projections 51 and 52, the recess being so located in the hub that it moves past either end face 42 or 43 of the respective leg 38 or 39. In the example illustrated, the recess is located in the hub so as to be moved past the end face 43 of the leg 39, the recess extending at right angles to the longitudinal direction of the hub 31. In a manner analogous to the variations shown in FIGS. 5 and 6, the recess can converge. In still another variation, also not illustrated, the recess 53 can be preceded in the direction of rotation by a recess having a smaller dimension than the recess 53, such as a smaller depth.

FIG. 9 shows still another embodiment for obtaining the desired change in flux. In this embodiment a magnet M3 of the magnets M' incorporates a notch 54, which moves past either the end face 42 or 43 of the respective leg 38 or 39 in the direction of rotation P. In the example illustrated, the notch is provided in the magnet M3 in the upper edge 55 thereof, which extends transversely to the axis 0. In the simplest case, shown in FIG. 10, the notch 54 extends at right angles from the edge 55. The leading edge of the control voltage has a favorable shape if, as shown in FIG. 11, the depth of the notch decreases in the direction of rotation. A stepped ignition advance is obtained with the variation shown in FIG. 12, in which the notch 54 is preceded, in the direction of rotation, by a smaller notch 56.

A magnetiferous extension piece 57 on the cross piece 46 of the magnet yoke, in the position shown, favorably influences the control and balance of the magnetic flux in the circuit. As shown in FIG. 13, the extension piece is preferably located in approximately the center of the cross piece and has a cross section that is at least approximately equal to that of the cross piece 46. The extension piece extends in the direction opposite that of the legs 38 and 39. If required, the extension piece, as shown in FIG. 14, can be provided with a magnetiferous transverse piece 58, which is positioned at least approximately in the projection of the cross piece In all of the embodiments thus far described, the magnetiferous cross piece 46 of the yoke H can be omitted, so that, as illustrated in FIG. 15, the yoke legs 38 and 39 are not magnetically coupled together. It is advisable, however, so as to fix the legs 38 and 39 in position, to connect the legs together by a non-magnetic cross piece 59. If a yoke of this kind is used with the embodiment shown in FIG. 1, it is possible in several different ways to prevent the internal combustion engine from turning over in the wrong direction.

With reference to FIG. 16, the winding section 25", which, when the engine turns in the wrong direction, produces a control voltage for the electronic switch 20 that normally would result in an ignition causing spark, is shunted by a diode 60,which is conductive when this control voltage appears. It is advisable, in order to ensure electrical symmetry, that the winding section 25 should be shunted by a diode 61 that is non-conductive when this generates a control voltage, because the engine is tuming in the right direction.

A second embodiment for preventing the engine from operating in the wrong direction P is shown in FIG. 17. In this form of the invention, the leg 39, which carries the winding section 25", also carries an auxiliary winding 62, which is connected in series with a diode 63 that conducts the current induced in the winding 25' when the engine turns in the wrong direction P and there is induced in the winding 25" a control voltage. With respect to the winding section 25", the auxiliary winding is wound in the opposite direction and is connected between the control terminal 24 and the reference terminal 26, the voltage induced in the auxiliary winding being sufficient to balance the control voltage induced in the winding section 25". For reasons. of electrical symmetry, it is advisable to connect the auxiliary winding 62 in series with a secondauxiliary winding 64, which is on the other leg 38. The second auxiliary winding 64 is connected between the control terminal 24 and the reference terminal 26 and is wound in the same direction as the winding section 25.

FIG. 18 shows the third embodiment for preventing rotation of the engine in the wrong direction. In this embodiment, a diode 65 forms, through the winding section 25', a series connection between the control terminal 24 and the reference terminal 26, the cathode of the diode 65 being connected to the end 49 of the winding section 25'. A second diode 66 forms a series connection, through the winding 25", between the reference terminal 26 and the control terminal 24, the cathode of this diode being connected to the end of the winding 25". When the magnetic system M rotates, the following occurs. With reference to the embodiment shown in FIG. 1, when the spacings Z are rotated past the end faces 34 and 35 of the iron core 29 that carries the alternating current winding 15, the changing flux in the core 29 induces an alternating current voltage in the winding 15. Those half waves of the alternating current voltage for which the diode 13 is conductive charge the ignition capacitor 11. Since the magnetic flux in the core 29 changes several times for each complete rotation of the magnetic system M, the ignition capacitor 11 is sufficiently charged to ensure a hot spark. If necessary, the ignition capacitor 11 can be charged through a full wave bridge rectifier, so that each half wave of the voltage induced in the alternating current winding 15 is used to charge the ignition capacitor 11.

In the present case, the ignition system is intended for a single cylinder internal combustion engine, so that, if the magnetic system rotates at the same speed as does the engine, there will be one ignition for each complete rotation of the magnetic system. This is ensured, because during one complete rotation of the magnetic system the extensions 40 and 41 are rotated past the yoke I! only once. From the voltage components that consequently are induced in the winding sections 25 and 25" there is obtained one complete cycle of alternating current voltage, that half wave thereof that is conducted by the diode 23 to the control electrode 22 of the switch triggering the latter. The ignition capacitor 11 can now discharge through the primary winding 17 of the spark coil 18, so as to induce in the secondary winding 27 a high voltage spike that produces a spark in the gap of the spark plug 28, which spark ignites the compressed fuel-air mixture in the cylinder of the engine.

When, in the embodiment shown in FIGS. 1 and 2, the active pole of a magnet M leaves the neighborhood of the end faces 42 and 43 of the legs 38 and 39 and is followed by another magnet M, there occurs, provided there are no extensions 40 and 41 in the open space Z separating these two magnets, a change in the flux density that chiefly takes place in the legs 38 and 39, the hub 31, the bottom of the body K, and in the short circuiting part 30. This change in the flux density induces voltage components in the winding sections and 25" that are balanced out because of the directions of winding of these two sections. Any lack of electrical balance, such as can be caused by the longer path taken by the flux that passes through the leg 38, is easily corrected by suitably varying the number of turns of the section 25 and 25" or by air gaps of the required size. The capacitor C shunted across the control winding 25 adds additional protection against the possible appearance of undesired interference voltages.

When the extensions 40 and 41 pass by the end faces 42 and 43 of the legs 38 and 39, there occurs a change in the density of the magnetic flux, which chiefly takes place only between the two extensions 40 and 41, and thus in the yoke legs 38 and 39 as well as in the cross piece 46. The voltage components consequently induced in the winding sections 25' and 25" result in one complete cycle of alternating current of which that half cycle conducted by the diode 23 triggers the electronic switch 20 to cause'ignition.

In explaining the embodiment shown in FIG. 3, it will first be assumed that a magnet M, which has just left the neighborhood of the cross piece 46, is followed by another magnet M, without there appearing opposite the end face 43 the magnetiferous projection 51. The resulting change in the flux density occurs chiefly in the legs 38 and 39, the hub 31, the bottom of the body K, and in the part 30. The voltage components induced in the windings 25' and 25" balance each other out because of the directions of winding of these two sections.

When the projection 51 passes by the end face 43 of the leg 39, the other end 39' of this leg is opposite the active pole -in the present case the S poleof a magnet M, the resulting increase and decrease in the flux through the leg 39 causing a complete cycle of altemating current voltage to be induced in the winding section 25". This voltage component is not balanced out, because at the same time the magnetic flux in the yoke leg 38 remains unchanged, there consequently being no voltage component induced in the winding section 25'. Consequently, that half period of the voltage induced in the winding section 25" conducted by the diode 23 is the control voltage for triggering the switch 20.

If the projection 51 has the shape shown in FIG. 5, the control voltage has a less steep leading edge, so that the ignition timing is adjustable over a widened range.

With the variation shown in FIG. 6, there is also produced a control voltage when the projection 52 passes by the end face 43 of the yoke leg 39. At low engine speeds, the peak amplitude of this control voltage is too small to trigger the switch 20, ignition being produced only when the projection 51 passes by the end face 43. When the engine rpm has risen to a predetermined value, the ignition is suddenly advanced, because the peak amplitude of the control voltage caused by the projection 52 is now sufficient to trigger the switch 20.

If the embodiment shown in FIGS. 7 and 8 is substituted for the projection 51 or the projections 51 and 52 of the preceding embodiments, there occurs in the leg 39 a decrease and than an increase in the magnetic flux, a full wave alternating current voltage being induced in the winding section 25 This induced voltage is not balanced out, because at the same time the magnetic flux in the leg 38 remains unchanged and no voltage is induced inthe winding section 25. Once again, that half wave that is conducted by the diode 23 is the control voltage that triggers the electronic switch.

In the embodiment shown in FIG. 9, it will first be assumed that the active pole of a magnet M has just passed by the neighborhood of the end faces 42and 43 and is followed by another magnet M that is now passing by these faces. The resulting change in flux density occurs chiefly in the legs 38 and 39, the hub 31, the bottom of the body K, and in the short circuiting part 30. The voltage components that are induced in the winding sections 25 and 25 are balanced out because of the winding directions of these sections.

When the magnet M3 with the notch (see FIG. 10) passes by the end face 43, the flux density-in the leg 39 decreases and then increases, inducing in the winding section 25" the voltage component in the. form of a complete cycle of alternating current voltage. This cycle of alternating current voltage is not compensated,

because at the same time the magnetic flux in the leg 38 remains unchanged, and no voltage is induced in the winding section 25. In this embodiment, as in the pre vious embodiments, that half wave that is conducted by the diode 23 triggers the electronic switch.

If the notch 54 has the shape shown in FIG. 11, the leading edge of the control voltage is less steep, so that the ignition timing s adjustable over a widened range.

In the embodiment shown in FIG. 12, the notch 56 also causes the generation of a control voltage, when this notch passes by the end face 43. At low engine speeds, however, the peak amplitude of the complete cycle of alternating voltage caused by this notch is too small to trigger the switch 20, the switch being triggered only when the notch 54 passes by the face 43. When the engine speed has reached a predetermined rpm, the ignition timing is suddenly advanced, becuase the amplitude of the control voltage caused by the notch 56 is now sufficient to trigger the switch 20.

When the yoke H in the embodiment shown in FIGS. 3 and 9 is replaced by the yoke 1-! shown in FIG. 15, the operation is the same as in the preceding embodiments: there is simply lacking the magnetiferous cross piece 56 that acts as a magnetic front, which enables the generation of higher voltages, but also of stronger interference voltages.

When the yoke H of the embodiment shown in FIGS. 1 and 2 is replaced by the embodiment shown in FIG. 15, the flux density varies as a magnet MI passes from the neighborhood of the end faces 42 and 43 and is followed, after the spacing Z, by the next magnet M1. If the aforesaid spacing 2 has no extensions 40 and 41, the flux density change occurs in the legs 38 and 39, the hub 31, the bottom of the body K, and the short circuiting part 30. Since the flux density changes in both of the yoke legs 38 and 39, voltage components are induced in the winding sections 25' and 25" that balance each other out.

When the extensions 40 and 41 pass by the end faces 42 and 43, the magnetic flux, as the active S pole of the magnet M1 leaves the neighborhood of the end face 42 and the active N pole of the magnet N2 enters this neighborhood, conducted through the hub 31, the bottom of the body K, and the short circuiting part 30 changes in the leg 38. This change induces in the winding section 25 a half wave of alternating current voltage, which is conducted by the diode 23 to trigger the switch. While this is occurring either the active S pole of the magnet M1 or the extension 40 thereof is opposite the end face 43, which fact prevents the generation of a compensating half wave of voltage, since the magnetic flux in the leg 39 remains unchanged, and no voltage can be induced in the winding section 25".

If of the magnet M1 the active S pole with the extension 40 leaves the neighborhood of the end face 43 and is followed by the active N pole of the magnet M2, the flux conducted through the hub 31, the bottom of the body K, and the short circuiting part 30 changes in the leg 39. The voltage consequently induced in the winding section 25 is blocked by the diode 23, so that the voltage generated cannot trigger the switch 20. While this is occurring, either the active N pole or the extension 41 of the magnet M2 is opposite the end face 42 of the leg 38. This prevents any compensation of the voltage half wave that is induced in the winding section 25", because the magnet flux in the leg 38 remains unchanged, and consequently no voltage can be induced in the winding section 25'.

If the engine --and thus the magnetic system M- turns in the wrong direction P, a voltage is induced in the winding section 25' that is blocked by the diode 23 and a voltage is induced in the winding section 25 that is conducted by the diode 23, when the extensions 40 and 41 move past theend faces 42 and 43 of the legs 38 and 39. in the embodiment shown in FIG. 16, no spark occurs at the spark plug, because the voltage appearing across the winding section 25" is short circuited by the diode 60. Consequently, the engine is effectively prevented from being operated in the wrong direction.

In the embodiment shown in FIG. 17, the voltage induced in the winding section 25" that ordinarily causes ignition when the engine turns in the wrong direction is opposed by the voltage half wave that is induced in the auxiliary winding 62 and is conducted by the diode 63. in this embodiment, as in the previous one, no ignition can occur if the engine turns in the wrong direction.

in the embodiment shown in FIG. 18, the diodes 65 and 66 and their connection to the winding sections 25' and 25" ensure that when the engine turns in the correct direction the control voltage induced in the winding section 25' is conducted by the diode 65 as well as by the diode 23, but that when the engine turns in the wrong direction the voltage halt wave induced in the winding section 25' which would otherwise trigger the switch 20, is blocked by the diode 66, which is connected in series with the winding section 25". When a spacing Z that has no extensions 40 and 40 passes by the end faces 42 and 43, the voltages induced in the winding sections 25' and 25" balance each other out.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions and circuits differing from the types described above.

While the invention has been illustrated and described as embodied in improvements in an internal combustion engine ignition system, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics 'of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. An electronic ignition arrangement for an internal combustion engine, comprising in combination an ignition capacitor; a transformer having a primary winding and a secondary winding; a spark plug connected across said secondary winding; an electronic switch having a control input and connected to said capacitor and to said primary winding to form with the latter a discharge path for said ignition capacitor; stationary support means; rotary support means mounted in proximity to said stationary support means for rotation about an axis of rotation; a charging winding mounted on said stationary support means and connected to said ignition capacitor for charging the latter; a yoke arrangement including two spaced legs of ferromagnetic material mounted on said stationary support means; a pair of windings each wound around a respective one of said legs and connected together to form a control winding connected across said control input for controlling the conductivity of said switch; first permanent magnet means on said rotary support means having a first field distribution and operative upon rotation of said rotary support means both for producing flux changes through said charging winding resulting in the flow of charging current into saidcapacitor and also for producing flux changes through said pair of windings resulting in the generation thereacross of opposing voltages preventing conduction by said switch; and second permanent magnet means on said rotary support means having a second field distribution and operative 'upon rotation of said rotary support means both for producing flux changesthrough said charging winding resulting in the flow of charging current into said capacitor and also for producing flux changes through said pair of windings resulting in the generation thereacross of a voltage rendering said switch conductive.

2. An arrangement as defined in claim 1, wherein said legs are parallel and extend in direction radially of said axis, and wherein said first and second permanent magnet means comprise a plurality of permanent magnets spaced about said axis and defining a cylinder.

3. The arrangement as defined in claim 1, wherein said yoke arrangement includes a magnetiferous cross piece physically connecting together said two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis.

4. The arrangement as defined in claim 1, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of said pair of windings when the engine turns in the correct direction.

5. The arrangement as defined in claim 1, wherein said two legs of said yoke arrangement are at least approximately bar-shaped members.

6. The arrangement as defined in claim 2, wherein said two legs are spaced apart in the direction parallel to said axis.

7. The arrangement as defined in claim 2, wherein said rotary support means includes a hub coaxialwith said axis, said hub rotating about said axis with said plurality of magnets, and further wherein said second magnet means includes at least a first magnetiferous projection on said hub for magnetically cooperating with one of said two legs of said yoke arrangement so as to vary, once during each complete rotation of said plurality of permanent magnets, the magnetic flux in said one leg while the magnetic flux in the other said leg is at least approximately unchanging.

8. The arrangement as defined in claim 2, .wherein said rotary support means includes a hub coaxial with said axis, said hub rotatating about said axis with said plurality of magnets, and further wherein said second magnet means includes at least a first recess in said hub for magnetically cooperating with one of said two legs of said yoke arrangement so as to vary, once during each complete rotation of said plurality of permanent magnets, the magnetic flux in said one leg while the magnetic flux in the other said leg is at least approximately unchanging.

9. The arrangement as defined in claim 2, wherein said second magnet means includes at least a first magnet, said first magnet being one of said plurality of permanent magnets, said first magnet incorporating at least a first notch for magnetically cooperating with one of said two legs of said yoke arrangement so as to vary, once during each complete rotation of said plurality of permanent magnets, the magnetic flux in said one leg while the magnetic flux in the other said leg is at least approximately unchanging.

10. The arrangement as defined in claim 2, wherein one end of the first control winding section is a control connection and one end of the second control winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or said reference connection and looking towards said common axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal.

11. The arrangement as defined in claim 1, wherein each magnet of said plurality of permanent magnets is polarized along a radius of said cylinder, successive magnets of said plurality of permanent magnets having alternating polarity.

12. The arrangement defined in claim 11, wherein said second permanent magnet means includes first and second neighboring permanent magnets, said plurality of permanent magnets including said first and second neighboring magnets, said first permanent magnet including an extension of one pole, said one pole being positioned nearer to said two legs when said first magnet is moved past said yoke arrangement than the other pole of said first magnet, said second permanent magnet including an extension of theother pole, said other pole being the opposite of said one pole and being positioned nearer to said two legs when said second magnet is moved past said yoke arrangement than the opposite pole of said second magnet, the two extensions projecting in circumferentially opposed directions into the common space between said first and second magnets, said two extensions being spaced apart, in a direction parallel to said axis, an amount equal to the spacing between said two legs so that in a predetermined rotational position of said plurality of permanent magnets each said extension is aligned with the end of a respective leg of said yoke arrangement.

13. The arrangement as defined in claim 12, including a respective magnetiferous plate covering that pole of each magnet of said plurality of permanent magnets that is positioned nearer to said yoke arrangement when the respective said magnet passes by the latter during rotation of said plurality of permanent magnets, the respective plate of said first and second magnets having a tongue constituting saidextension, the surfaces of the two tongues at least approximately defining part of a common cylindrical surface having as its axis said axis of rotation.

14. The arrangement as defined in claim 12, wherein said rotary support means includes a magnetiferous hollow cylindrical housing, said plurality of permanent magnets being mounted within said housing in physical contact within the surface thereof, said'housing including a central hub for accepting a driven shaft to rotate said housing, said hub being coaxial with said axis, and further wherein said yoke arrangement includes a magnetiferous cross piece physically connecting together said two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis, said cross piece being positioned directly opposite said hub.

15. The arrangement defined in claim 12, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of the two control winding sections when the engine turns in the correct direction, further wherein one end of the first winding section is a control connection and one end of the second winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or from said reference connection and looking toward said axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal, the other end of said first winding section and the other end of said second winding section being connected together, and further wherein a first diode is shunted across the other of said first and second winding sections across which said control voltage is generated when the engine turns in the wrong direction, said first diode being connected so as to short circuit said other of said first and second windings when the engine turns in the wrong direction, whereby no control voltage is generated and the engine is prevented from operating in the wrong direction.

16. The arrangement defined in claim 12, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of the two control winding sections when the engine turns in the correct direction, further wherein one end of the first winding section is a control connection and one end of the second winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or from said reference connection and looking toward said axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal, the other end of said first winding section and the other end of said second winding section being connected together, and further including a first auxiliary winding on that one of said legs that carries the other of said first and second winding sections across which said control voltage is generated when the engine turns in the wrong direction, said first auxiliary winding connected between said control connection and said reference connection, a diode connected in series with said first auxiliary winding so as to conduct when the engine turns in the wrong direction, said first auxiliary winding being wound in the opposite direction with respect to said other of said first and second winding sections and having a number of turns sufficient to balance out the control voltage induced in said other of said first and second winding sections, whereby there is no control voltage present to cause the engine to turn in the wrong direction.

17. The arrangement as defined in claim 12, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of the two control winding sections when the engine turns in the correct direction, and further wherein one end of the first winding section is a control connection and one end of the second winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or from said reference connection and looking toward said common axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal, and further including a first diode connected in series between the other end of said first winding section and said reference connection; a second diode connected in series between the other end of said second winding section and said control connection, the anode of said first diode being connected to said reference connection and the anode of said second diode being connected to said control connection.

18. The arrangement as defined in claim 15, further wherein a second diode is shunted across said one of said first and second section windings, said second diode being connected so as to be non-conductive when the engine turns in the correct direction, whereby said control voltage can appear across said one of said first and second section windings.

19. The arrangement as defined in claim 16, further including a second auxiliary winding, said second auxiliary winding being carried on the other of said two legs, said second auxiliary winding being wound in the same direction as said one of said first and second winding sections and being connected in series with said first auxiliary winding and between said control connection and said reference connection.

20. The arrangement as defined in claim 7, wherein said magnetiferous projection in a predetermined rotational position of said plurality of permanent magnets is radially aligned with said one leg, said projection being fixedly radially aligned with that pole of a magnet of said plurality of magnets that is nearer to said projection.

21. The arrangement as defined in claim 7, wherein said magnetiferous projection converges towards said hub in the direction of rotation of the latter.

22. The arrangement as defined in claim 7, further including a second magnetiferous projection positioned on said hub so as to precede said first projection in the direction of rotation of said plurality of magnets, said second projection varying to a smaller degree, at any given engine speed, the flux through said one leg than said first projection so as to advance the spark when the engine speed exceeds a predetermined rpm.

23. The arrangement as defined in claim 8, wherein said recess in a predetermined rotational position of said plurality of permanent magnets is radially aligned with said one leg, said recess being fixedly radially aligned with that pole of a magnet of said plurality of magnets that is nearer to said recess.

24. The arrangement as defined in claim 7, wherein said yoke arrangement includes a magnetiferous cross piece physically connecting together said two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis, said corresponding ends of said two legs being spaced farther from said hub than the opposite ends of said two legs.

25. The arrangement as defined in claim 8, wherein said arrangement yoke includes a magnetiferous cross piece physically connecting together sadi two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis, said corresponding ends of said two legs being spaced farther from said hub than the opposite ends of said two legs.

26. The arrangement as defined in claim 3, wherein said cross piece includes a magnetiferous extension piece that projects from said cross piece in the direction opposite to that of said two legs.

27. The arrangement as defined in claim 26, wherein said extension piece has a cross section at least approximately the same as that of said cross piece.

28. The arrangement as defined in claim 26, wherein said extension piece is located approximately in the center of said cross piece and projects at right angles therefrom.

29. The arrangement as defined in claim 26, wherein said extension piece includes a transverse piece that is located at least approximately within the projection of said cross piece.

30. The arrangement as defined in claim 9, wherein the depth of said notch decreases in the direction of rotation of said plurality of magnets.

31. The arrangement as defined in claim 9, including a second notch located in said first magnet so as to precede said first notch in the direction of rotation of said plurality of magnets, said second notch varying to a smaller degree, at any given engine speed, the flux through said one leg than said first notch so as to ad- 15 16 vance the spark when the engine speed exceeds a pre- 33. The arrangement as defined in claim 10, further determined including a capacitor connected between said refer- 32. The arrangement as defined in claim 10, wherein the other end of said first control winding section and the other end of said second control winding section Pres-5mg mterference voltagesare connected together.

ence connection and said control connection for sup- 

1. An electronic ignition arrangement for an internal combustion engine, comprising in combination an ignition capacitor; a transformer having a primary winding and a secondary winding; a spark plug connected across said secondary winding; an electronic switch having a control input and connected to said capacitor and to said primary winding to form with the latter a discharge path for said ignition capacitor; stationary support means; rotary support means mounted in proximity to said stationary support means for rotation about an axis of rotation; a charging winding mounted on said stationary support means and connected to said ignition capacitor for charging the latter; a yoke arrangement including two spaced legs of ferromagnetic material mounted on said stationary support means; a pair of windings each wound around a respective one of said legs and connected together to form a control winding connected across said control input for controlling the conductivity of said switch; first permanent magnet means on said rotary support means having a first field distribution and operative upon rotation of said rotary support means both for producing flux changes through said charging winding resulting in the flow of charging current into said capacitor and also for producing flux changes through said pair of windings resulting in the generation thereacross of opposing voltages preveNting conduction by said switch; and second permanent magnet means on said rotary support means having a second field distribution and operative upon rotation of said rotary support means both for producing flux changes through said charging winding resulting in the flow of charging current into said capacitor and also for producing flux changes through said pair of windings resulting in the generation thereacross of a voltage rendering said switch conductive.
 2. An arrangement as defined in claim 1, wherein said legs are parallel and extend in direction radially of said axis, and wherein said first and second permanent magnet means comprise a plurality of permanent magnets spaced about said axis and defining a cylinder.
 3. The arrangement as defined in claim 1, wherein said yoke arrangement includes a magnetiferous cross piece physically connecting together said two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis.
 4. The arrangement as defined in claim 1, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of said pair of windings when the engine turns in the correct direction.
 5. The arrangement as defined in claim 1, wherein said two legs of said yoke arrangement are at least approximately bar-shaped members.
 6. The arrangement as defined in claim 2, wherein said two legs are spaced apart in the direction parallel to said axis.
 7. The arrangement as defined in claim 2, wherein said rotary support means includes a hub coaxial with said axis, said hub rotating about said axis with said plurality of magnets, and further wherein said second magnet means includes at least a first magnetiferous projection on said hub for magnetically cooperating with one of said two legs of said yoke arrangement so as to vary, once during each complete rotation of said plurality of permanent magnets, the magnetic flux in said one leg while the magnetic flux in the other said leg is at least approximately unchanging.
 8. The arrangement as defined in claim 2, wherein said rotary support means includes a hub coaxial with said axis, said hub rotatating about said axis with said plurality of magnets, and further wherein said second magnet means includes at least a first recess in said hub for magnetically cooperating with one of said two legs of said yoke arrangement so as to vary, once during each complete rotation of said plurality of permanent magnets, the magnetic flux in said one leg while the magnetic flux in the other said leg is at least approximately unchanging.
 9. The arrangement as defined in claim 2, wherein said second magnet means includes at least a first magnet, said first magnet being one of said plurality of permanent magnets, said first magnet incorporating at least a first notch for magnetically cooperating with one of said two legs of said yoke arrangement so as to vary, once during each complete rotation of said plurality of permanent magnets, the magnetic flux in said one leg while the magnetic flux in the other said leg is at least approximately unchanging.
 10. The arrangement as defined in claim 2, wherein one end of the first control winding section is a control connection and one end of the second control winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or said reference connection and looking towards said common axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal.
 11. The arrangement as defined in claim 1, wherein each magnet of said plurality of permanent magnets is polarized along a radius of said cylinder, successive magnets of said plurality of permanent magnets having alternating polarity.
 12. The arrangement defined in claim 11, wherein said second permanent maGnet means includes first and second neighboring permanent magnets, said plurality of permanent magnets including said first and second neighboring magnets, said first permanent magnet including an extension of one pole, said one pole being positioned nearer to said two legs when said first magnet is moved past said yoke arrangement than the other pole of said first magnet, said second permanent magnet including an extension of theother pole, said other pole being the opposite of said one pole and being positioned nearer to said two legs when said second magnet is moved past said yoke arrangement than the opposite pole of said second magnet, the two extensions projecting in circumferentially opposed directions into the common space between said first and second magnets, said two extensions being spaced apart, in a direction parallel to said axis, an amount equal to the spacing between said two legs so that in a predetermined rotational position of said plurality of permanent magnets each said extension is aligned with the end of a respective leg of said yoke arrangement.
 13. The arrangement as defined in claim 12, including a respective magnetiferous plate covering that pole of each magnet of said plurality of permanent magnets that is positioned nearer to said yoke arrangement when the respective said magnet passes by the latter during rotation of said plurality of permanent magnets, the respective plate of said first and second magnets having a tongue constituting said extension, the surfaces of the two tongues at least approximately defining part of a common cylindrical surface having as its axis said axis of rotation.
 14. The arrangement as defined in claim 12, wherein said rotary support means includes a magnetiferous hollow cylindrical housing, said plurality of permanent magnets being mounted within said housing in physical contact within the surface thereof, said housing including a central hub for accepting a driven shaft to rotate said housing, said hub being coaxial with said axis, and further wherein said yoke arrangement includes a magnetiferous cross piece physically connecting together said two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis, said cross piece being positioned directly opposite said hub.
 15. The arrangement defined in claim 12, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of the two control winding sections when the engine turns in the correct direction, further wherein one end of the first winding section is a control connection and one end of the second winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or from said reference connection and looking toward said axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal, the other end of said first winding section and the other end of said second winding section being connected together, and further wherein a first diode is shunted across the other of said first and second winding sections across which said control voltage is generated when the engine turns in the wrong direction, said first diode being connected so as to short circuit said other of said first and second windings when the engine turns in the wrong direction, whereby no control voltage is generated and the engine is prevented from operating in the wrong direction.
 16. The arrangement defined in claim 12, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of the two control winding sections when the engine turns in the correct direction, further wherein one end of the first winding section is a control connection and one end of the second winding sEction is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or from said reference connection and looking toward said axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal, the other end of said first winding section and the other end of said second winding section being connected together, and further including a first auxiliary winding on that one of said legs that carries the other of said first and second winding sections across which said control voltage is generated when the engine turns in the wrong direction, said first auxiliary winding connected between said control connection and said reference connection, a diode connected in series with said first auxiliary winding so as to conduct when the engine turns in the wrong direction, said first auxiliary winding being wound in the opposite direction with respect to said other of said first and second winding sections and having a number of turns sufficient to balance out the control voltage induced in said other of said first and second winding sections, whereby there is no control voltage present to cause the engine to turn in the wrong direction.
 17. The arrangement as defined in claim 12, wherein said yoke arrangement includes a non-magnetiferous cross piece physically connecting together said two legs so that a control voltage is generated across one of the two control winding sections when the engine turns in the correct direction, and further wherein one end of the first winding section is a control connection and one end of the second winding section is a reference connection, said first and second winding sections being wound in the same direction as seen either from said control connection or from said reference connection and looking toward said common axis, the number of turns of said first and second winding sections being such that said opposing voltages are at least approximately equal, and further including a first diode connected in series between the other end of said first winding section and said reference connection; a second diode connected in series between the other end of said second winding section and said control connection, the anode of said first diode being connected to said reference connection and the anode of said second diode being connected to said control connection.
 18. The arrangement as defined in claim 15, further wherein a second diode is shunted across said one of said first and second section windings, said second diode being connected so as to be non-conductive when the engine turns in the correct direction, whereby said control voltage can appear across said one of said first and second section windings.
 19. The arrangement as defined in claim 16, further including a second auxiliary winding, said second auxiliary winding being carried on the other of said two legs, said second auxiliary winding being wound in the same direction as said one of said first and second winding sections and being connected in series with said first auxiliary winding and between said control connection and said reference connection.
 20. The arrangement as defined in claim 7, wherein said magnetiferous projection in a predetermined rotational position of said plurality of permanent magnets is radially aligned with said one leg, said projection being fixedly radially aligned with that pole of a magnet of said plurality of magnets that is nearer to said projection.
 21. The arrangement as defined in claim 7, wherein said magnetiferous projection converges towards said hub in the direction of rotation of the latter.
 22. The arrangement as defined in claim 7, further including a second magnetiferous projection positioned on said hub so as to precede said first projection in the direction of rotation of said plurality of magnets, said second projection varying to a smaller degree, at any given engine speed, the flux thrOugh said one leg than said first projection so as to advance the spark when the engine speed exceeds a predetermined rpm.
 23. The arrangement as defined in claim 8, wherein said recess in a predetermined rotational position of said plurality of permanent magnets is radially aligned with said one leg, said recess being fixedly radially aligned with that pole of a magnet of said plurality of magnets that is nearer to said recess.
 24. The arrangement as defined in claim 7, wherein said yoke arrangement includes a magnetiferous cross piece physically connecting together said two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis, said corresponding ends of said two legs being spaced farther from said hub than the opposite ends of said two legs.
 25. The arrangement as defined in claim 8, wherein said arrangement yoke includes a magnetiferous cross piece physically connecting together sadi two legs at corresponding ends thereof, said cross piece extending at least approximately parallel to said axis, said corresponding ends of said two legs being spaced farther from said hub than the opposite ends of said two legs.
 26. The arrangement as defined in claim 3, wherein said cross piece includes a magnetiferous extension piece that projects from said cross piece in the direction opposite to that of said two legs.
 27. The arrangement as defined in claim 26, wherein said extension piece has a cross section at least approximately the same as that of said cross piece.
 28. The arrangement as defined in claim 26, wherein said extension piece is located approximately in the center of said cross piece and projects at right angles therefrom.
 29. The arrangement as defined in claim 26, wherein said extension piece includes a transverse piece that is located at least approximately within the projection of said cross piece.
 30. The arrangement as defined in claim 9, wherein the depth of said notch decreases in the direction of rotation of said plurality of magnets.
 31. The arrangement as defined in claim 9, including a second notch located in said first magnet so as to precede said first notch in the direction of rotation of said plurality of magnets, said second notch varying to a smaller degree, at any given engine speed, the flux through said one leg than said first notch so as to advance the spark when the engine speed exceeds a predetermined rpm.
 32. The arrangement as defined in claim 10, wherein the other end of said first control winding section and the other end of said second control winding section are connected together.
 33. The arrangement as defined in claim 10, further including a capacitor connected between said reference connection and said control connection for suppressing interference voltages. 